Non-resetting thermally responsive switch



G. F. EBENSTEINER 3,246,107

NON-RESETTING THERMALLY RESPONSIVE SWITCH Filed Nov. 4, 1963 April 12, 1966 O 4. l. 4 s 2 4 w.. Jl. 2 Irl.. e 2 mw m .WwW-m o F .l A x s m M 4 H 4.

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w L m m B INVENTOR. GERALD F. EBENSTEINER F IG. 4

ATTORNEYS FIG. 3

United States Patent O 3,246,107 NON -RESETTING THERMALLY RESPONSIVE SWITCH Gerald F. Ebensteiner, Minneapolis, Minn., assignor, by

mesne assignments, to United-Carr Incorporated, Boston, Mass., a corporation of Delaware Filed Nov. 4, 1963, Ser. No. 321,211 Claims. (Cl. 200-138) This invention relates generally to thermally responsive switches, and pertains more particularly to snap-acting thermal switches of the type that are not automatically reset.

In certain situations, it is imperative that there be no malfunctioning of components due to an excessive temperature rise. Such a temperature rise can impair either the present or the 'fu-ture reliability of a particular component even though it might continue to perform its task for `a while. Space exploration is but one area where eX- treme care must be exercised lto assure that various components continue to operate and that any possibility of temporary or permanent damage be detected immediately. Even in certain types of industrial control a hi-gh degree of reliability is demanded in order to avoid costly shutdowns or lossV of equipment.

Accordingly, one object of the invention is to provide a :switch that will provide a reliable switching action when a given temperature condition is reached. More specifically, it is an .aim of the invention to provide a snap-acting switch Athat will produce a change of contact position that does not return to its previous state even when the temperature has been reduced to a normal level. In other words, it is within the purview of the present invention to provide a switch that is not automatically reset.

Another object is to provide a snai -acting thermally responsive switch that Iwil-l in effect have a double snap- 'acting capability. This is derivable lfrom a bimetallic member that lirst changes curvature with ya snap action followed by a snapping spring action of the electrical contacts carried thereon. g vA further object of the invention is to provide a reliable switch vof the foregoing character that can be miniaturized "for use in compact environments and which can be inexpensively manufactured, thecost being sufficiently low that' in certain applications the switch might even be discarded once it has b eent-ripped due to an undesired temperature having been reached.y

These and'other objects and yadvantages of my invention will more fully appear from the following description, made in connection with the accompanying drawing, wherein like reference characters refer to the same or similar parts throughout the several views and in which:

IFIGURE 1 is an elevational view in section of one form my switch may assume, the view showing the switch contacts. in' a latched condition under normal temperature y conditions;

FIGURE 2 is a -vielw corresponding to FIGURE 1 but with the switch having been subjected rto a sufficient temperature rise to cause fthe bimetallic disc to become reversely ilexed with a concomitant change in contact position from Athat. depicted in FIGURE 1;

FIGURE 3 shows the .bimetallic disc after it has cooled and returned to its original shape but with .the contacts still remaining in a changed or tripped position, and

FIGURE 4 is a perspective view of the bimetallic disc with the spring contact arms carried thereon pictured in their unrestrained position before the disc is placed in its casing.

Referring now in det-ail to the drawing, the switch exemplifying my invention comprises a cup-shaped cap 110 of plastic material, such as polystyrene, and a plug or base 12 of similar material, the cap and base having co- 3,246,107 Patented Apr. 12, 1966 ICC operable threads at 14 so that the base can be removed if desired to do so. It will be noted that the base 12 is formed with a relatively large recess 18 extending upwardly from its bottom surface 20. Stated somewhat differently, the bottom surface 20 of the base 1.2 is cornposed of annular steps or shoulders 16, 18.

A iirst pair of contact posts 22 are tiXedly retained in the plug yor base 12, these posts having notches 24 in their lower ends. Similarly retained in the base 1-2 is a second pair of contact posts 26 having notches 28 in their lower ends.

Within a Acompartment formed between the bottom of the cap 10 and the bottom of the base :12 is disposed a dish-shaped or concavo-convex bimetallic disc 30 comprised or layers 32, 34 of met-al having different temperature coefficients of expansion. As shown, -the layer 34 has a greater coetlicient than the layer 32 so that under normal or relatively cool conditions the disc is bowed upwardly (see FIGURES 1 and 3) but under adverse or relatively hot conditions the disc is bowed downwardly (see FIGURE 2).

A strip 36 of resilient metal has its central or bight portion 38 secured, .as by spot welding, to the center of the disc 30. The strip 36 includes upwardly diverging contact spring arms 40 having angled tips 42 at the free ends thereof. The normal or unrestrained angular relationship of these arms 40 is best viewed in FIGURE 4.

'The plug or base 12 is provided with at least two, and preferably more, lugs 44 that serve to hold the peripheral edges of the disc 30 in place, .thereby preventing any shifting of the disc 30 within the cap 10. The cap 10, in the illustrated instance, has an opening 46 for the entrance of heat, but obviously the cap 10 can be made sufiiciently heat conductive so that the opening would not be employed. In practice, it will sometimes be desirable to have a lag or time delay .present so that ithe switch does not immediately operate but instead operates only when a Aprolonged adverse temperature condition prevails; the

material for the cap -10 can be selected in accord-ance with the heat transfer coefficient that is desired 'and the proper wall thickness can be also determined for desired functioning.

Although it should be evident that the exemplary switch will iind utility in a number of applications where either a signal or a control of an electrically energized comlponent or device is involved, for the sake of simplicity a simplified signaling system has been presented. The system has a first battery 48 and a lamp 50 connected in series between the contact posts 22. A second battery 54 is connected in series with a lamp 52 between the second pair of posts 26.

In use, the switch will be assembled by first inverting the spring arms 40 are then ilexed or squeezed suiciently together with an appropriate tool or implement so that the tips 42 canV be inserted into the notches 24 of the contact posts 22. lThen the base 12 is turned through degrees and placed in the cap 10, rotation thereof then effecting the relationship shown in FIGURE l.

Assuming that the switch is connected as shown and described, when the disc 3l) reaches a certain temperature, it snaps from the upwardly convexed position of FIG- URE 1 to the downwardly convexed position of FIG- URE 2. In so doing, the bight 38 of the strip 36 is moved downwardly to such an extent that the tips 42 are withdrawn from the notches 16 of the contact posts 22 with the consequence that the circuit to the lamp 50 is interrupted. Owing to the inherent resiliency of the arms 40, the arms spring apart to achieve this action.

Due to the foregoing spring action, the circuit to the lamp 52 is then closed via the tips 42 and the contact posts 26, thereby indicating that the switch has been actuated or tripped. Thus, when the lamp 5i) is lighted, the observer knows that no excessive temperature increase has been experienced, and when the lamp 52 becomes energized he knows that such a temperature has occurred.

It should be emphasized that an exceedingly rapid contact disengagement is realized by virtue of the fact that the snap action of the disc 30 downwardly from the position shown in FIGURE 1 to that shown in FIGURE 2 is immediately followed by an outward springing of the contact arms 40V in a direction away from the contact posts 22.l This is not only desirable from an operational standpoint but helps to prolong the life of the contacts by eliminating damaging arcs, thereby permitting the switch to be reused many times if desired.

Assuming that the temperature causing the disc 30 to bow downwardly decreases enough, then the disc will return to its original upwardly dished coniiguration pictured in FIGURE 3, which is the same as that illustrated in FIGURE l. However, the tips 42 on the spring arms ride against the sides of the contact posts 26 as the disc 30 tlexes upwardly and lodge themselves in the notches 28 formed on these particular posts 26. It is to be expressly understood that the contact arms 40 cannot cause engagement again of their tips 42 with the contact posts 22. Hence, there is absolutely no possibility that the circuit to the lamp 50 will be re-established.

In this way, an observer will know that an adverse temperature condition has been reached and he can take `the proper steps to replace the component that may have been damaged by heat or he may merely make a check on the component. It will be understood that the switch will be placed in a proximal relationship with the component or device it is to protect. In some instances, it will be desired to merely check a particular maximum allowable temperature that has been reached in a cubicle or compartment housing a number of components, and the switch herein described will perform this supervisory roll very effectively. Also in shipping merchandise, excessive temperatures can be easily noted. Thus, the invention will have considerable versatility as far as its particular uses are concerned.

It will, of course, be understood that various changes may be made in the form, details, arrangements and proportions of the parts without departing from the scope of my invention as set forth in the appended claims.

What is claimed:

1. A snap-acting thermally responsive switch comprisi ing:

(a) a bimetallic disc member normally convex in one direction but capable of assuming an oppositely convex appearance when subjected to sufcient heat;

(b) a resilient strip having its central portion secured to the central portion of one side of said disc member and providing oppositely inclined contact spring arms;

(c) means providing a pair of spaced notches having a xed distance therebetween less than the normal unrestrained distance between the free ends of said spring arms, said notches receiving said free ends and thereby flexing said free ends toward each other, and

(d) means outwardly adjacent said notches for engaging said free ends to prevent their return to said notches after said disc has assumed its said oppositely convex appearance.

2. A snap-acting thermally responsive switch comprising:

(a) casing means providing a compartment;

(b) a -bimetallic disc disposed in said compartment and having irst and second convex positions depending upon the temperature to which, said disc is subjected:

(c) a resilient strip having an intermediate portion thereof secured to a central portion of one sideof saidY disc to provide diverging contact springs arms;

(d) a pair of spaced contact posts extending through said casing means and each having a notch at its inner'endV for receiving the free end of one arm to flex said armstoward each other;

(d) said. casing means having an inwardly facing surface for preventing the re-engagement `of said free ends with said notches after said disc has reached its said second convex position.

3. A snap-acting thermally responsive switch in accordance with claim 2 including:

(a) a second pair of contact posts spaced laterally outwardly with respect to said iirst pair,

(b) said second pair of contact posts having notches for the reception of said free ends after said disc has returned to its said first convex position.

4. A non-resetting thermally responsive switch comprising:

(a) a heat responsive element having a first position at one temperature and a second position at another temperature;

(b) resilient contact means secured to said heat responsive element and providing a pair of contact springv arms;

(c) means for retaining said spring arms in a first spaced relation to each other when said heat responsive element is in its rst position and for releasing said spring arms to move to a second spaced relation upon motion of said heat responsive element to its second position; and

(d) means for preventing return of said spring arms to their rst spaced relation.

5. A non-resetting thermally responsive switch as recited in claim 4, wherein (a) said contact spring arms are in electrical communication with one another; and

(b) said retaining means includes stationary contact means engaged by said spring arms in at least one of their spaced relations.

References Cited by the Examiner UNITED STATES PATENTS 1,920,806 S/l933 Rich 20G-122 2,496,332 2/1950 Carle 200--116 2,856,487 10/1958 Manz 200-116 BERNARD A. GILHEANY, Primary Examiner. 

1. A SNAP-ACTING THERMALLY RESPONSIVE SWITCH COMPRISING: (A) A BIMETALLIC DISC MEMBER NORMALLY CONVEX IN ONE DIRECTION BUT CAPABLE OF ASSUMING AN OPPOSITELY CONVEX APPEARANCE WHEN SUBJECTED TO SUFFICIENT HEAT; (B) A RESILIENT STRIP HAVING ITS CENTRAL PORTION SECURED TO THE CENTRAL PORTION OF ONE SIDE OF SAID DISC MEMBER AND PROVIDING OPPOSITELY INCLINED CONTACT SPRING ARMS; (C) MEANS PROVIDING A PAIR OF SPACED NOTCHES HAVING A FIXED DISTANCE THEREBTWEEEN LESS THAN THE NORMAL UNRESTRAINED DISTANCE BETWEEN THE FREE ENDS OF SAID SPRING ARMS, SAID NOTCHES RECIEVING SAID FREE ENDS 